12. your friend with great excitement tells you about his newest idea to solve the energy crisis: he wants to use an electromotor to drive a generator and then use part of the electric power generated to power the electromotor while using the rest to power his home. what would you tell him?

I would tell him, in the kindest, most gentle way I could manage,
to fahgeddaboudit. 

The total amount of energy doesn't change.  Energy is never created,
and it never disappears.  If you have some energy, then it had to come
from somewhere, and if you used some energy, then it had to go
somewhere. 

You can never get more energy out of the electromotor than you put into it,
 and in the real world, you can't even get THAT much out, because some
of it is always used on the way through.

Pour yourself a cold glass of soda, then look up "Perpetual Motion" or
"Free Energy" on the internet, relax, and enjoy the show.  They are all
fakes.  They may not all be intentionally meant to fool you, but they are
all impossible.